Conventional manholes include a lower or bottom pad, a barrel having a relatively constant diameter adjacent the pad, a concentric or eccentric cone extending upwardly from the barrel, one or more adjusting rings to adjust the overall height of the manhole, and a casting frame on top of the adjusting rings to support a lid at an elevation substantially level with the surrounding pavement. The casting frame is preferably sealed to the uppermost adjusting ring to preclude or minimize water flow into the manhole.
One problem with existing manholes is that many were made long ago, and then oftentimes were made of brick. Due to the old age of the manholes, as well as the materials used to make them, many manholes have begun to deteriorate or have damaged areas. The damaged areas create weak spots, which may allow water to infiltrate the sewer system and also lead to the eventual collapse of the manhole.
Methods exist for repairing the walls of manholes. One such method involves the use of a cured-in-place (CIP) liner with a polymer coating on its interior surface and a bladder to repair the manhole wall. The liner and bladder are placed in the manhole, and the bladder is expanded to press the liner against the manhole wall. The liner is impregnated with a resin and applied to the wall to create a new interior wall of the manhole. One problem with existing methods is the size of the liner used to line the wall of the manhole. The methods call for the use of a CIP liner and bladder having a diameter approximately equal to the smallest diameter of the manhole, with the liner being capable of stretching circumferentially to press against the manhole wall so to prevent the liner from wrinkling. However, some manholes require that the liner stretch up to and exceeding 150% of its unstretched diameter. This can cause the liners to rip, tear or be too thin, leaving the manhole wall not fully repaired.
Additionally, because the liners include an interior coating impervious to a resinous material, the liners cannot fold over themselves or bunch up because the liner wall would be formed with intermediate layers of material impervious to resin causing the liner to not be homogeneous across its thickness.
Accordingly, there is a need in the art for an improved method and means that overcomes the problem of a liner tearing while stretching circumferentially to press against the wall of a manhole.